Pneumatic vibrator and starting system therefor



Feb. 19, 1957 P E 2,781,742

PNEUMATIC VIBRATOR AND STARTING SYSTEM THEREFOR Filed Aug. 21, 1953 2 Sheets-Sheet 1 THEN.

- .34 34% T' l' INVENTOR [an 4R1) M P0046 ATTORN EY Feb. 19, 1957 LE 2,781,742

PNEUMATIC VIBRATOR AND STARTING SYSTEM THEREFOR Fil ed Aug. 21, 1953 2 Sheets-Sheet 2 INVENTOR [aw/1,70 4 1/ 004:

ATTQRNEY PNEUMATIC VIBRATOR AND STARTING SYSTEM THEREFQR Edward-M. Poole, Barberton, Ohio, assignor to The Babcock & Wilcox Company, New York, N, Y., a corporation :of New Jersey Application Augustin, 1953, Serial No.'375,638

4;.Claims. (Cl. 12117) This inventionrelates to vibrators-and, more particularly,ito a novel, improved-pneumatic vibrator and a starting system-therefor.

Vibrators. of thezpneumatic type generally comprise a cyclinder having a relatively massive piston reciprocable therein, and include means; forapplying fluid pressure alternately to opposite. ends of the piston. to eflect such reciprocation. Due to the: relatively. high inertiav of the piston; the pistonv remains stationaryand the cylinder is reciprocated'relativeto the piston. T o utilize such vibration or reciprocation of thecylinder, the latter is attached to the structure to be vibrated and. may be resiliently supported :for axial reciprocation.

Whensuch'pneumatic vibratorsare positioned for vibration in a substantially horizontal plane, special starting arrangements are incorporated. One arrangement; which is widely used involves a startingspring-which, when, the pressure fluid supply is cut ofli, biases the piston to one end of the. cylinder. Thus, when the vibrator is restarted, the pressure fluid is admitted to such one end of the cylinder first. In another known arrangement, a spring positioned valve is provided to assure the proper sequence of pressure fluid application in starting the vibrator.

The foregoing starting arrangements are generally satisfactory in normal operation but, over relatively long periods of time, spring breakage becomes an important maintenance factor. .The spring'breakage is accelerated when these pneumatic vibrators are usedin heavy duty applications or under severe operating conditions.

A typical exampleuof such. conditions is represented by the use of pneumatic vibrators to periodically-shake or vibrate suspended .tubesections of a vapor .generatorto dislodge .combustion gasrdeposited solids from-the tube; surfaces. Due to the relatively high ambienttemperatures involved in installations of this type, vibrators incorporating starting springsareunsatisfactory due to'the necessity for. frequent .spring replacement. This is not only costly in time'andlabor but; also;incr,eases the down time"of the vibrator withconsequent potentialv buildup. of deposited solids to a point affectingefficient operation of the generator section.

As a solution of thesedifilculties, thepresent invention provides a pneumatic. vibrator in which no starting? springs or springoperatedstarting valves arefused. The

two pressure fluid inlet ports in the cylinder side wall, re

spectively selectively communicating with opposite ends of the cylinder,- are provided with separate valve controlled supply linesconnectedto the source of pressure fluid. In starting the vibrator, only one valve is opene'dinitially, thus providing initial fluid pressure application to only. oneend of the cylinder. After. a preset time interval, tor example 3 seconds; the second-valve: is opened. .Both valves Qthenf remain open during the vibrating period, which may continue tor a. preselected time duration.

In a practicahapplication, the secondvalve is operated by time delay means activated simultaneously with operation. oilthel first valve. 'T he.first valve, and the time ,de-

atent L lay means, are, in turn, preferably operated by a timer combination which periodically initiates operation of the vibrator at preset times, and maintains the vibrator operating for a predeterminedinterval.

For an understanding of the invention priciples, reference is made to the following-description of a typical practical embodimentthereof as illustrated in the accompanying drawings.

in the drawings:

Fig. 1 is an axial sectional view through a pneumatic vibrator embodying theinvention and schematically indicating the pressure fluid supply lines;

Fig. 2 is a diametric sectional view on the line 22 of of'Fig. l;

Fig. 3 is a partiaielevation. view of a vaporgenerator suspended tube bank having the inventionvibrator attac-hedv thereto; and

, Fig.4 is aschematic wiring diagram'of the. vibrator starting andtiining system. i

Referring to Figs. 1- and 2, the invention pneumatic vibrator i comprises a. cylinder Zilin vwhich is reciproca-' bly mountedv a relatively, massive, high inertia pistonvv40t Cylinder Zii comprises a cylindrical Wall 21, with longitu-' dinalreinforcing ribs 22 extending therealong, andinteg-ral, end flangesZSiQrmed. with bolt openings 24 at each corner. Tghis .integral-structure is assembled with imperforate or closed: end walls; 25, 25 byrneans of boltand nut as semblies fidextending through both-WaHs-ZS andthrough theholesgZ-i in flanges 23,- gasketsl? being interposed; between each flange 2 3 and the adiacent endwall 25, The end walls 2Sare angular, having legs or flanges 28; .provided with openings 31 to; receive bolts 32 for attachment of the vibrator to asupport 33 (Figs. 1 and 3).

Side wall 21 has fornied-therethrough inlet ports-39o, 36b and exhaust ports 35a, 35b, the inlet ports. each having. ani'enlarged, threaded recess 34 for connection-of a pressure fluid line thereinto. As best seen in. Fig. 2, each inlet port includes a series of drilled passages.36 at the, inner end of recess 34, and each exhaust port .com-.. prises dual, circumferentially spaced passage 37., 37.

The inletports a and 39b are spaced equal distances from adjacent endwalls 215, and exhaust ports a and 35b are intermediate the inlet ports and symetrically located relative to the rnid-point of the cylinder. The purpose of these dispositions will be explained hereinafter.

Piston 40 is formed with reduced end sections 41a, and 41b and a pairtof circumferential g'rooves45rz, b spaced axiallyfrom each other a distance substantially less than the axial spacing of inlet ports 30a, 30b but greater than the axial sp'acingof. exhaust ports,35a, 35b. '1" he groove 45a is connected by three radial passages 42a tothree longitudinal passages (5a extending through end 41a. Similarly,.three' radialpassagesffib connect groove Sb to three longitudinal passages 43b extending through end 41b.

In the positionillustrated in Fig. 1,,piston 4915 at the left end of cylinder 20,-and groove 45a registers with, inlet port 3%. This is one of iseveral possible starting positions of the vibrator. As schematically illustrated-inEig. l, a pressurefluidsupply line filfcontrolledby a valve 50, is connected to port Spa, and a separate pressurefluid supply line 56, controlled by a valve 5'5, is connected to port 30b.

i T 0 start the vib'rator'from the position shown in Fig. 1, control valve 59 is opened, admitting pressure fluid through line 51, inlet port'3tia, groove 45a; and passages 42a, 43a to the left end of. piston 40. Piston ld is thus forced to the right, it beingnoted that groove 45b is registered with exhaust. port 35b when piston 40 isatthe left end of the cylinder 2t As piston 40 moves to the right, inlet portfitlaand exhaust port 35:1 am blockedoff, but piston movement continues, due to'the' inertia of the piston, to register groove 45:: with exhaust port 35a and groove 45b with inlet port 30b.

Meanwhile, a preset time interval after valve 50 is opened, valve 55 is opened to admit pressure fiuid through line 56 to inlet port 3012. Thus, as groove 45b registers with port 305, pressure fluid is admitted through groove 45b and passages 42b, 43b to the right end of the piston. Consequently, as piston 40 approaches the right end of the cylinder, pressure is building up at this end while being exhausted from the left end through the registry of groove 45a with exhaust port 3511.

The piston is now forced to the right, cutting 01f port 30b and then registering groove 45b with exhaust port 35b. The cycle now repeats, both valves 50 and 55 remaining open during the desired operating period of the vibrator. To stop the vibrator, both control valves are closed. Re-starting is always efiected by first opening only the valve 50 and then opening valve 55 a preset time after valve 50 is opened, for example 3 seconds.

If it is assumed that piston 40 has stopped in mid position, or equi-distant from both ends of cylinder 20, the drilled inlet passages 36 for ports 30a and 30b will be adjacent to the piston grooves 45a and 45b, as will also be the exhaust passages 35a and 35b. Piston 40 has running clearance in cylinder 20, as will be understood by those skilled in the art. Thus, when control valve 50 is opened to supply air through line 51 to inlet port 30a and through the drilled passage 36 communicating therewith, the air will flow between the piston and cylinder in the clearance space therebetween. At least some of this air will flow through passages 42a and 43a to the left end of the piston and some of the air will flow toward exhaust port 35a through piston groove 45a. Due to the fact that the inlet ports are located on the opposite side of the cylinder from the exhaust port, the entering air under pressure displaces the piston 40 toward the exhaust ports, pressing it against cylinder wall 21 to effectively increase the resistance to flow of air to the exhaust ports. Accordingly, the air pressure is effectively exerted in the cylinder on the left face of the piston, increasing the pressure on this face and forcing the piston to the right. After a short movement to the right, cylinder groove 45b will register with passage 36 of inlet port 3012. After the preset time interval, valve 55 opens and air will flow through line 56 to inlet port 30b and thus through passage 36, groove 45b and passages 42b and 43b to the right end of the cylinder forcing the piston 40 to the left. With both valves 50 and 55 now open, operation of the piston proceeds in the manner previously described.

Should the piston 40 have stopped at the right end of cylinder 20, when valve 50 is opened the air entering through port 30a will again flow into the clearance between the piston and cylinder, pushing the piston toward the exhaust ports, and also flowing through groove 45a through exhaust port 35a. The piston remains substantially stationary until valve 55 opens after the preset time interval. When valve 55 opens, the air will flow through inlet port 30b to the right end of the piston to move the piston to the left, the air entering through port 30a being ineffective to resist this movement due to the communication between groove 45a and exhaust port 35a.

Fig. 3 illustrates a typical installation of vibrator 10. The member 33 is a sleeve having a rod 61 telescoped therethrough with its inner end connected to one or more tubes 62 of a heat exchanger section 60, such as a superheater section of a steam generator. Blocks 63 on member 33 are positioned against each leg 28 of end walls 25, and a bracket 64 connects rod 61 to tubes 62.

The sleeve 33 is mounted through a liner 65 in a port through the casing wall 66 of the steam generator, being supported from liner 65, with leakage of air through the opening between member 33 and liner 65 prevented by seam member 67. The outer end of sleeve 33 is suspended, by aspring 68, from a supporting framework partially illustrated at 70, spring 68 being secured to a collar 71 on sleeve 33. A coil spring 72 surrounds the outer end of rod 61, seated at one end against collar 71 and at the other end against a spring seat 73 adjustably positioned along rod 61 by nuts 74 threaded on the rod.

In operation, as piston 40 is reciprocated relative to cylinder 20, the piston remains substantially stationary due to its relatively large inertia, and the cylinder is vibrated. This vibration is transmitted to sleeve 33 and rod 61, and thus to tubes 62. The latter are thus vibrated to dislodge cornbustion-gas-deposited solids from their surfaces.

Referring to Fig. 4, a preferred electrical control system for starting the vibrator at periodic intervals and operating the vibrator for a set time duration each time it is started, is illustrated as energized from conductors 76, 76 connected across an A. C. supply through switches 75 ganged for conjoint operation. When switches 75 are closed, a timer 77 is energized, this timer having an indicating lamp 78 connected in parallel with its motor 79. The latter, through suitable reduction gearing, drives a cam 81 which periodically closes a normally open switch 82.

When switch 82 is closed, it energizes a duration of operation timer 80. This timer has a clutch 83 which, after a preset interval of operation, opens normally closed switches 84, 86. Switch 84 is in series with the motor 87 of timer and switch 86 is in series with a relay 90. Thus, when switch 82 closes, relay 90 is energized to close its contacts 91. These contacts are in series with solenoid valve 50 in supply line 51, and also in series with a time delay relay 95. An indicating lamp 92 is in shunt with valve 50.

After a time delay of from 3 to 20 seconds, relay 95 closes its contacts 96 which are in series with solenoid valve 55 in supply line 56, and having an indicating lamp 97 in shunt therewith. Vibrator 10 is started by the opening of valve 50, and continues to vibrate as long as valves 50 and 55 remain open, valve 55 being opened by time delay relay 95 preferably 3 seconds after valve 50 is opened by closing of relay contacts 91.

After an operating period of up to 60 seconds, clutch 83 opens switches 84, 86 to stop timer 80 and drop relay 90. When relay 90 drops, opening of contacts 91 closes valve 50 and drops relay 95. Opening of relay contacts 96 closes valve 55. The vibrator then stops until the interval timer 77 again closes contacts 82 to restart the vibrating cycle.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A pneumatic vibrator comprising, in combination, a cylinder having closed end walls; a relatively massive piston reciprocably mounted in said cylinder; first and second inlet ports in the side wall of said cylinder; first passage means in said piston opening through one end thereof and communicating with said first port when said one end of the piston is adjacent the corresponding end of said cylinder; second passage means in said piston opening through the opposite end thereof and communicating with said second port when said opposite end of the piston is adjacent the opposite end of said cylinder; exhaust port means in the side wall of said cylinder intermediate said inlet ports; first valve means selectively operable to connect a source of pressure fluid to said inlet port to move said piston toward such opposite end of said cylinder to initiate relative reciprocation between said piston and cylinder to vibrate said cylinder; second valve means operable to connect a source of pressure fluid to said second inlet ports; time delay means activated upon operation of said first valve means to operate said second valve means a preset time interval after operation of said first valve means; and a cyclically op erable timer operatively associated with said first valve means and said time delay means to periodically and simultaneously operate said first valve means and activate said time delay means for a predetermined time interval.

2. A pneumatic vibrator comprising, in combination, a cylinder having closed end walls and constructed for connection to a structure to be vibrated; means mounting said cylinder for axial reciprocation; a relatively massive piston reciprocably mounted in said Cylinder; first and second inlet ports in the side Wall of said cylinder; first passage means in said piston opening through one end thereof and communicating with said first port when said one end of the piston is adjacent the corresponding end of said cylinder; second passage means in said piston opening through the opposite end thereof and communicating with said second port when said opposite end of the piston is adjacent the opposite end of said cylinder; first valve means selectively operable to connect a source of pressure fluid to said first inlet port to move said piston toward such opposite end of said cylinder to initiate relative reciprocation between said piston and cylinder to vibrate said cylinder; second valve means operable to connect a source of pressure fluid to said second inlet port; time delay means activated upon operation of said first valve means to operate said second valve means a preset time interval after operation of said first valve means; and a cyclically operable timer operatively associated with said first valve means and said time delay means to periodically and simultaneously operate said first valve means and activate said time delay means for a predetermined time interval.

3. A pneumatic vibrator comprising, in combination, a cylinder having closed end walls; a relatively massive piston reciprocably mounted in said cylinder; first and second inlet ports in the side Wall of said cylinder; first passage means in said piston opening through one end thereof and communicating with said first port when said one end of the piston is adjacent the corresponding end of said cylinder; second passage means in said piston opening through the opposite end thereof and communicating with said second port when said opposite end of the piston is adjacent the opposite end of said cylinder; exhaust port means in the side wall of said cylinder intermediate said inlet ports; a first solenoid valve selectively operable to connect a source of pressure fluid to said first inlet port to move said piston toward such opposite end of said cylinder to initiate relative reciprocation between said piston and cylinder to vibrate said cy l' inder; a second solenoid valve operable to connect a source of pressure'fluid to said second inlet port; and time delay means energized simultaneously with said first solenoid valve to energize said second solenoid valve a pre-set time interval after energization of said first solenoid valve.

4. A pneumatic vibrator comprising, in combination, a cylinder having closed end walls; a relatively massive piston reciprocably mounted in said cylinder; first and second inlet ports in the side wall of said cylinder; first passage means in said piston opening through one end thereof and communicating with said first port when said one end of the piston is adjacent the corresponding end of said cylinder; second passage means in said piston opening through the opposite end thereof and communieating with said second port when said opposite end of the piston is adjacent the opposite end of said cylinder; exhaust port means in the side Wall of said cylinder intermediate said inlet ports; a first solenoid valve selectively operable to connect a source of pressure fluid to said first inlet port to move said piston toward such opposite end of said cylinder to initiate relative reciprocation between said piston and cylinder to vibrate said cylinder; a second solenoid valve operable to connect a source of pressure fluid to said second inlet port; time delay means energized simultaneously with said first sole noid valve to energize said second solenoid valve a preset time interval after energization of said first solenoid valve; and a cyclically operable timer operatively associated with said first solenoid valve and said time delay means to periodically and simultaneously energize said first solenoid valve and said time delay means for a predetermined time interval.

References Cited in the file of this patent UNITED STATES PATENTS 1,872,403 Cannon Aug. 16, 1932 2,590,155 Cannon Mar. 25, 1952 

